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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Forces Generated by High Velocity Impact of Ice on a Rigid Structure

Tests were conducted to measure the impact forces generated by cylindrical ice projectiles striking a relatively rigid target. Two types of ice projectiles were used, solid clear ice and lower density fabricated ice. Three forms of solid clear ice were tested: single crystal, poly-crystal, and "rejected" poly-crystal (poly-crystal ice in which defects were detected during inspection.) The solid ice had a density of approximately 56 lb/cu ft (0.9 gm/cu cm). A second set of test specimens, termed "low density ice" was manufactured by molding shaved ice into a cylindrical die to produce ice with a density of approximately 40 lb/cu ft (0.65 gm/cu cm). Both the static mechanical characteristics and the crystalline structure of the ice were found to have little effect on the observed transient response. The impact forces generated by low density ice projectiles, which had very low mechanical strength, were comparable to those of full density solid ice. This supports the hypothesis that at a velocity significantly greater than that required to produce fracture in the ice, the mechanical properties become relatively insignificant, and the impact forces are governed by the shape and mass of the projectile.

Pereira, J. Michael↗
NASA NTRS2020

Polarimetric Radar Characteristics of Simulated and Observed Intense Convective Cores for a Midlatitude Continental and Tropical Maritime Environment

This study contrasts midlatitude continental and tropical maritime deep convective cores using polarimetric radar observables and retrievals from selected deep convection episodes during the MC3E and TWPICE field campaigns. The continental convective cores produce stronger radar reflectivities throughout the profiles, while maritime convective cores produce more positive differential reflectivity Z(dr) and larger specific differential phase K(dp) above the melting level. Hydrometeor identification retrievals revealed the presence of large fractions of rimed ice particles (snow aggregates) in the continental (maritime) convective cores, consistent with the Z(dr) and K(dp) observations. The regional cloud-resolving model simulations with bulk and size-resolved bin microphysics are conducted for the selected cases, and the simulation outputs are converted into polarimetric radar signals and retrievals identical to the observational composites. Both the bulk and the bin microphysics reproduce realistic land and ocean (L-O) contrasts in reflectivity, polarimetric variables of rain drops, and hydrometeor profiles, but there are still large uncertainties in describing Zdr and Kdp of ice crystals associated with the ice particle shapes/orientation assumptions. Sensitivity experiments are conducted by swapping background aerosols between the continental and maritime environments, revealing that background aerosols play a role in shaping the distinct L-O contrasts in radar reflectivity associated with raindrop sizes, in addition to the dominant role of background thermodynamics.

Toshihisa Matsui↗
NASA NTRSDate not supplied

Application of Lidar-Radar Combined Data Products during the IMPACTS 2020 Field Campaign

The Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) is a three-year field campaign investigating the formation and lifecycle of banded, precipitation structures within intense wintertime cyclones impacting the highly-populated northeast United States. Unlike previous campaigns in the region, IMPACTS mission scientists have access to and coordinate the NASA ER-2 and P-3 aircraft to collect observations from both a remote sensing and in-situ perspective, respectively. For IMPACTS, the ER-2 aircraft was equipped with lidar (CPL), radar (CRS, HIWRAP, EXRAD), microwave radiometer (CoSMIR, AMPR) instruments, each with their own unique capabilities and limitations. Our on-going work effort aims to develop IMPACTS lidar and radar merged data products, which can be used to supplement the raw data sources, tease out additional aspects of the mechanisms underpinning wintertime cyclones, and enhance our understanding of microphysical properties in sensor overlap regions. Preliminary merged data products combine CPL lidar with any one of the NASA High Altitude Radar (HAR) radar products (CRS, HIWRAP, EXRAD) and represent these data as both normalized values and translated to reflectivity signal (dB). Continuing work will further refine our merged data product algorithm to provide additional information on hydrometeor species identification, ice crystal habit, and ice-water content, which will help IMPACTS achieve its mission goal of improving microphysical properties retrievals from both airborne and spaceborne platforms.

Stephen D. Nicholls↗
NASA NTRS1989

Cirrus optical depth retrieval from satellite-measured bidirectional reflectance

In the framework of investigating the relationship between the visible optical depth and microphysics of cirrus clouds, the doubling scheme for radiative transfer in cirrus cloudy atmospheres, as developed by Takano and Liou (1988), has been used to compute the bidirectional reflectances at the top of the atmosphere. Reflectance data taken at about the same time from GOES and AVHRR over Waussau, as well as particle distributions observed during the FIRE IFO carried out in Wisconsin (1986) were the basis of the experiment. For the cirrus microphysical model, hexagonal ice crystals and area-equivalent ice spheres are considered. The single scattering phase functions for randomly oriented hexagonal columns and area-equivalent ice spheres are computed from geometric optics and Mie theory, respectively.

Takano, Y.↗
NASA NTRS2021

An Investigation of the Grain Size and Adhesion Strength of High-Speed Impact Ice

Ice accumulation on aircraft from supercooled water droplets (impact icing) can increase drag and decrease lift, leading to a decrease in fuel efficiency and a potential for unsafe situations. Anti-icing materials and coatings are of high interest to prevent aircraft icing. Because no anti-icing material suitable for in-flight situations has been realized, icing models aim to predict the accumulation and shape of the ice to understand its effects. In both cases, understanding the physical mechanism behind ice adhesion and shedding is necessary. A recent literature review has shown that the apparent ice adhesion strength to any specific material varies over several orders of magnitude across studies and test methods. One of the reasons for this high variance is likely to be the varying microstructure of the ice used for different studies. Although the microstructure of impact ice has been studied in the past, those conditions were not relevant to that of in-flight aircraft icing. The microstructure of the ice formed will determine both its bulk and surface properties, yet it has been overlooked in the ice adhesion community. Here, we use optical microscopy to study the non-uniform ice crystal grain size in impact ice accreted in NASA Glenn Research Center’s Icing Research Tunnel at various icing conditions. Similar to other environmental conditions studied in the literature, we show an increase in grain size at larger distances from the growth interface; however, the data shows substantially larger grains than what was expected from the prior literature. Ice accrued at lower temperatures has a smaller grain size at all distances from the growth interface. No change in grain size was noticed when varying only the wind speed. A correlational analysis shows that smaller grain sizes at the growth interface corresponded to an increase in the apparent ice adhesion strength when the adhesive failure was interfacial, but not when the failure was cohesive. These results may explain the overall trend in the literature of increasing apparent adhesion strength with decreasing temperature. Incorporating microstructure trends for various environmental conditions in icing models may increase the certainty in predicting ice adhesion strength and shedding, and will provide a better basis for comparison between adhesive tests on ice produced in different facilities and at different storage times.

• Ice Fabric↗
NASA NTRS1991

A numerical study of thunderstorm electrification - Model development and case study

A numerical model was developed for examining the thunderstorm electrification process in which it is assumed that the electrification is entirely due to noninductive charge transfer between colliding ice crystals and hail. Since this ice-hail charge mechanism is very dependent on particle sizes and distributions, an explicit microphysical framework is used. To maintain simplicity, the electrification model is kinematic; thus the temperature and velocity fields are input into the electrification model. The cloud model of Taylor (1989) was used to generate the temperature and velocity fields to examine the July 19, 1981, Cooperative Convective Precipitation Experiment thundercloud. Using these fields, the electrification model produced time-dependent ice particle concentrations, radar reflectivities, charge, and vertical electric field distributions in good general agreement with those observed. The model produced a maximum electric field strength of 1.27 kV/cm, which is on the order of that needed for lightning initiation, and this maximum occurred very close to the time of the observed discharge. Thus, the ice-hail charge mechanism appears to have played an important role in the electrical development of the July 19 cloud.

Norville, K.↗
NASA NTRS2010

Examination of Icing Induced Loss of Control and Its Mitigations

Factors external to the aircraft are often a significant causal factor in loss of control (LOC) accidents. In today s aviation world, very few accidents stem from a single cause and typically have a number of causal factors that culminate in a LOC accident. Very often the "trigger" that initiates an accident sequence is an external environment factor. In a recent NASA statistical analysis of LOC accidents, aircraft icing was shown to be the most common external environmental LOC causal factor for scheduled operations. When investigating LOC accident or incidents aircraft icing causal factors can be categorized into groups of 1) in-flight encounter with super-cooled liquid water clouds, 2) take-off with ice contamination, or 3) in-flight encounter with high concentrations of ice crystals. As with other flight hazards, icing induced LOC accidents can be prevented through avoidance, detection, and recovery mitigations. For icing hazards, avoidance can take the form of avoiding flight into icing conditions or avoiding the hazard of icing by making the aircraft tolerant to icing conditions. Icing detection mitigations can take the form of detecting icing conditions or detecting early performance degradation caused by icing. Recovery from icing induced LOC requires flight crew or automated systems capable of accounting for reduced aircraft performance and degraded control authority during the recovery maneuvers. In this report we review the icing induced LOC accident mitigations defined in a recent LOC study and for each mitigation describe a research topic required to enable or strengthen the mitigation. Many of these research topics are already included in ongoing or planned NASA icing research activities or are being addressed by members of the icing research community. These research activities are described and the status of the ongoing or planned research to address the technology needs is discussed

Reehorst, Andrew L.↗
NASA NTRS2013

Influence of Ice Particle Surface Roughening on the Global Cloud Radiative Effect

Ice clouds influence the climate system by changing the radiation budget and large-scale circulation. Therefore, climate models need to have an accurate representation of ice clouds and their radiative effects. In this paper, new broadband parameterizations for ice cloud bulk scattering properties are developed for severely roughened ice particles. The parameterizations are based on a general habit mixture that includes nine habits (droxtals, hollow/solid columns, plates, solid/hollow bullet rosettes, aggregate of solid columns, and small/large aggregates of plates). The scattering properties for these individual habits incorporate recent advances in light-scattering computations. The influence of ice particle surface roughness on the ice cloud radiative effect is determined through simulations with the Fu-Liou and the GCM version of the Rapid Radiative Transfer Model (RRTMG) codes and the National Center for Atmospheric Research Community Atmosphere Model (CAM, version 5.1). The differences in shortwave (SW) and longwave (LW) radiative effect at both the top of the atmosphere and the surface are determined for smooth and severely roughened ice particles. While the influence of particle roughening on the single-scattering properties is negligible in the LW, the results indicate that ice crystal roughness can change the SW forcing locally by more than 10 W m(exp −2) over a range of effective diameters. The global-averaged SW cloud radiative effect due to ice particle surface roughness is estimated to be roughly 1-2 W m(exp −2). The CAM results indicate that ice particle roughening can result in a large regional SW radiative effect and a small but nonnegligible increase in the global LW cloud radiative effect.

clouds↗
NASA NTRS2021

Operational Detection of Sun Glints in DSCOVR EPIC Images

Satellite images often feature sun glints caused by the specular reflection of sunlight from water surfaces or from horizontally oriented ice crystals occurring in clouds. Such glints can prevent accurate retrievals of atmospheric and surface properties using existing algorithms, but the glints can also be used to infer more about the glint-causing objects—for example about the microphysical properties and radiative effects of ice clouds. This paper introduces the recently released operational glint product of the Earth Polychromatic Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft. Most importantly, the paper describes the algorithm used for generating the key component of the new product: a glint mask indicating the presence of sun glint caused by the specular reflection of sunlight from ice clouds and smooth water surfaces. After describing the glint detection algorithm and glint product, the paper shows some examples of the detected glints and discusses some basic statistics of the glint population in a yearlong dataset of EPIC images. These statistics provide insights into the performance of glint detection and point toward possibilities for using the glint product to gain scientific insights about ice clouds and water surfaces.

DSCOVR↗
NASA NTRS2018

Deep Space Observations of Sun Glint from Oceans

Every hour or two, the Earth Polychromatic Imaging Camera (EPIC) onboard the DSCOVR satellite provides unique full-color images of the sunlit side of the Earth from the L1 Lagrangian point, which is four times farther the Moon. Casual glances at such images often reveal bright colorful spots that stand out markedly from their surroundings. Such spots often appear not only over ocean but also over land. Tracking the colorful spots using an automated image analysis algorithm reveals that they are caused by specular reflection of sunlight, sometimes from ocean surfaces and other times from clouds containing horizontally oriented ice crystals. The presented study characterizes these spots in terms of prevalence, location, color, and brightness, and provides insights into the factors that lead to their appearance.

ice crystals↗
NASA NTRS1984

Ice depolarization on low-angle 2 GHz satellite downlinks

The impact of ice depolarization on the statistical performance of satellite downlinks were investigated. Propagation data recorded during 1979 and 1980 to see what impact of ice depolarization on link performance were analyzed. The effects on the cross polarization discrimination (XPD) statistics amounted to at most a 2 to 4 dB reduction in the XPD values which rain would have produced for a given percentage of time. Ice depolarization had no effect on the statistics of XPD values below the 0.01% level. Most of the severe ice depolarization events were associated with drops in barometric pressure and the passage of intense cold fronts through our area. Ice contents as the product of three individually undetermined quantities were defined: ice particle density, ice cloud thickness, and the average volume of the ice crystals. It is indicated that populations of ice particle with ice contents on the order of 0.002 m4/m3 are probably responsible for the lower values of measured XPD.

Stutzman, W. L.↗
NASA NTRSDate not supplied

Analysis of Hot-Wire Probe Ice Water Content Measurements in High Ice Water Content Conditions

During the 2022 High Ice Water Content (HIWC) Flight Campaign, ice water content (IWC) measurements were made at various locations on the NASA DC-8 Airborne Science Laboratory using the Isokinetic Probe Version 2 (IKP2), Ice Crystal Detectors (ICD), and Robust Probe. Correlations of a wing mounted ICD to IKP2 were made to determine the collision/retention efficiency of the ICD total water content (TWC) element in glaciated conditions. Similarly, correlations of a nose mounted ICD near the pitot probes were made to the IKP2 and to the wing-mounted ICD to estimate the ice concentration factor near the DC-8 pitot probes. Results from the 2022 flight campaign were compared to results from the HIWC RADAR II flight campaign in 2018. There was an apparent reduction in the ICD TWC collision/retention efficiency during the 2022 flight campaign. Although reasons for this discrepancy were explored, more analyses are needed to fully understand the causes. However, it was concluded that an estimated ice concentration factor at the nose of 2.5 was consistent between the two flight campaigns. Additionally, a correlation model was developed to relate measurements from a Nose ICD to freestream IWC as measured by the IKP2 to support IWC measurements from the 2022 Convective Processes Experiment - Cabo Verde (CPEX-CV) flight campaign.

Icing↗
NASA NTRSDate not supplied

Analysis of Hot-Wire Probe Ice Water Content Measurements in High Ice Water Content Conditions

During the 2022 High Ice Water Content (HIWC) Flight Campaign, ice water content (IWC) measurements were made at various locations on the NASA DC-8 Airborne Science Laboratory using the Isokinetic Probe Version 2 (IKP2), Ice Crystal Detectors (ICD), and Robust Probe. Correlations of a wing mounted ICD to IKP2 were made to determine the collision/retention efficiency of the ICD total water content (TWC) element in glaciated conditions. Similarly, correlations of a nose mounted ICD near the pitot probes were made to the IKP2 and to the wing-mounted ICD to estimate the ice concentration factor near the DC-8 pitot probes. Results from the 2022 flight campaign were compared to results from the HIWC RADAR II flight campaign in 2018. There was an apparent reduction in the ICD TWC collision/retention efficiency during the 2022 flight campaign. Although reasons for this discrepancy were explored, more analyses are needed to fully understand the causes. However, it was concluded that an estimated ice concentration factor at the nose of 2.5 was consistent between the two flight campaigns. Additionally, a correlation model was developed to relate measurements from a Nose ICD to freestream IWC as measured by the IKP2 to support IWC measurements from the 2022 Convective Processes Experiment - Cabo Verde (CPEX-CV) flight campaign.

Icing↗
NASA NTRS1977

Effect of ice contamination of liquid-nitrogen drops in film boiling

Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. Experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation is presented. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

Schoessow, G. J.↗
NASA NTRS1977

Effect of ice contamination on liquid-nitrogen drops in film boiling

Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. This paper presents experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

Schoessow, G. J.↗
NASA NTRS2017

A Dynamic Model for the Evaluation of Aircraft Engine Icing Detection and Control-Based Mitigation Strategies

Aircraft flying in regions of high ice crystal concentrations are susceptible to the buildup of ice within the compression system of their gas turbine engines. This ice buildup can restrict engine airflow and cause an uncommanded loss of thrust, also known as engine rollback, which poses a potential safety hazard. The aviation community is conducting research to understand this phenomena, and to identify avoidance and mitigation strategies to address the concern. To support this research, a dynamic turbofan engine model has been created to enable the development and evaluation of engine icing detection and control-based mitigation strategies. This model captures the dynamic engine response due to high ice water ingestion and the buildup of ice blockage in the engines low pressure compressor. It includes a fuel control system allowing engine closed-loop control effects during engine icing events to be emulated. The model also includes bleed air valve and horsepower extraction actuators that, when modulated, change overall engine operating performance. This system-level model has been developed and compared against test data acquired from an aircraft turbofan engine undergoing engine icing studies in an altitude test facility and also against outputs from the manufacturers customer deck. This paper will describe the model and show results of its dynamic response under open-loop and closed-loop control operating scenarios in the presence of ice blockage buildup compared against engine test cell data. Planned follow-on use of the model for the development and evaluation of icing detection and control-based mitigation strategies will also be discussed. The intent is to combine the model and control mitigation logic with an engine icing risk calculation tool capable of predicting the risk of engine icing based on current operating conditions. Upon detection of an operating region of risk for engine icing events, the control mitigation logic will seek to change the engines operating point to a region of lower risk through the modulation of available control actuators while maintaining the desired engine thrust output. Follow-on work will assess the feasibility and effectiveness of such control-based mitigation strategies.

engine control↗
NASA NTRS2017

A Dynamic Model for the Evaluation of Aircraft Engine Icing Detection and Control-Based Mitigation Strategies

Aircraft flying in regions of high ice crystal concentrations are susceptible to the buildup of ice within the compression system of their gas turbine engines. This ice buildup can restrict engine airflow and cause an uncommanded loss of thrust, also known as engine rollback, which poses a potential safety hazard. The aviation community is conducting research to understand this phenomena, and to identify avoidance and mitigation strategies to address the concern. To support this research, a dynamic turbofan engine model has been created to enable the development and evaluation of engine icing detection and control-based mitigation strategies. This model captures the dynamic engine response due to high ice water ingestion and the buildup of ice blockage in the engines low pressure compressor. It includes a fuel control system allowing engine closed-loop control effects during engine icing events to be emulated. The model also includes bleed air valve and horsepower extraction actuators that, when modulated, change overall engine operating performance. This system-level model has been developed and compared against test data acquired from an aircraft turbofan engine undergoing engine icing studies in an altitude test facility and also against outputs from the manufacturers customer deck. This paper will describe the model and show results of its dynamic response under open-loop and closed-loop control operating scenarios in the presence of ice blockage buildup compared against engine test cell data. Planned follow-on use of the model for the development and evaluation of icing detection and control-based mitigation strategies will also be discussed. The intent is to combine the model and control mitigation logic with an engine icing risk calculation tool capable of predicting the risk of engine icing based on current operating conditions. Upon detection of an operating region of risk for engine icing events, the control mitigation logic will seek to change the engines operating point to a region of lower risk through the modulation of available control actuators while maintaining the desired engine thrust output. Follow-on work will assess the feasibility and effectiveness of such control-based mitigation strategies.

engine control↗